The aim of the “Therapy Evaluation Project” was to examine the therapy outcomes of all violent and sex offenders treated by the Zurich Criminal Justice System between January 1997 and the 31st of December 2005.

This included all the court-ordered therapies at the prisons of the Canton of Zurich as well as outpatient treatments that were carried out after release from detention (or instead of detention). The final treatment sample consisted of N=222 treated violent and sex-offenders. A representative sample of untreated violent and sex-offenders served as a control group.

After a mean time at risk of six years, the recidivism rates of the offenders were reviewed. Two types of recidivism were defined:

1. (1) The listing of a new conviction in the criminal record or

2. (2) offense relevant behaviour documented by the therapists, the probation services and/or other authorities.

The recidivism rate for treated violent and sex-offender was 12% compared to 20% for the untreated controls. By juxtaposing the various criteria/definitions of recidivism, the standards for evaluating the effectiveness of therapy will be debated.